Pregnancy termination with a high and medium dosage regimen of RU 486.

Sixty healthy pregnant women who wished to terminate their pregnancy and who were no more than 49 days pregnant were treated with one of three different dose regimens of a synthetic progesterone receptor blocker, RU 486. Serum cortisol was measured to determine the antiglucocorticoid effects of this compound. The high dose but shorter treatment regimen (400 mg/day RU 486 X 4 days or 200 mg/day X 4 days) was associated with a high (greater than 80%) rate of side effects, especially nausea, vomiting, weakness and heavy bleeding and a low rate of success (10%). A group of 50 subjects received the medium dose but longer treatment regimen (100 mg/day X 7 days). This group had less side effects (40-60%) and a 72.3% success rate of complete abortion. The AM cortisol values were significantly elevated in all treatment groups but higher in those receiving the high dose. These values returned to normal one week following cessation of treatment. Medium dose but longer duration (100 mg/day X 7 days) of RU 486 treatment is associated with a higher success rate and less side effects than higher dose therapy administered over a shorter period. There were no predictive indices to determine which subjects would respond successfully. The reason for the failure of the drug in 30% of the subjects on the medium dose is not known at this time.